Pressing means for ready-to-use winding unit



April 30, 1968 H. urz 3,381,252

PRESSING MEANS FOR READY-TO---USE WINDING UNIT Filed Dec. 1, 1965 5 Sheets-Sheet 1 INVENTOR. HEINRICH LUTZ ATTORNEYS.

April 30, 1968 H. LUTZ 3,38

PRESSING MEANS FOR READY-TO-USE WINDING UNIT Filed Dec. 1, 1965 5 Sheets-Sheet 2 I lllllllll lllllll F 5 INVENTOR.

HEINRICH LUTZ A T TORNE Y$ April 30, 1968 H. LUTZ 3,381,252

PRESSING MEANS FOR READY-TO-USE WINDING UNIT Filed Dec. 1, 1965 a Sheets-Sheet 5 1 N VEN TOR. HEINRICH L U TZ ATTORNEY-5'.

United States Patent 3,381,252 PRESSING MEANS FOR READY-TO-USE WINDING UNIT Heinrich Lutz, Dubendorf, Switzerland, assignor to Maschinenfabrik Oerlikon, Zurich, Switzerland Filed Dec. 1, 1965, Ser. No. 510,806 Claims priority, application Switzerland, Dec. 10, 1964, 15,991/64; Dec. 24, 1964, 16,685/64 8 Claims. (Cl. 336-197) This invention relates to ready-to-use winding units of the type including a winding and pressing means engaged with the winding to restrain the same against distortion due to stresses resulting from short circuit currents and the like, whereby a winding unit is provided which can be mounted as a unit on a magnetic core and the like. More particular, the present invention is directed to novel pressing means for such a winding unit.

A known form of winding unit of the type to which the present invention is directed has a pair of annular pressure plates with each plate engaged with 1 respective axial end surface of an annular winding, and the two plates are interconnected by metal tie rods. This known unit, however, is impractical for use with high voltages by virtue of the problems involved in providing insulation against flash-over and the like. Additionally, the tie rods constitute a rigid connection between the pressure plates and, if the rods are of unequal length and if they are unequally stressed, substantial radial shearing forces may act on the winding, particularly during relatively large short circuits.

In transformers having the conventional concentric arrangement of the low and high voltage windings, it is possible to use tie rods only within the low voltage windings, again due to the necessity for providing proper insulation against flash-over between thetwindings and the tie rods. Tie rods located exterior to the high voltage winding would have to be spaced so far from the latter that it would be impractical to use the same for reasons of space considerations. If tie rods are used only on the inside of the low voltage windings, these tie rods, as well as the pressure plates common to both the low voltage and high voltage windings, must be made very rugged to insure a reliable restraint on the windings.

Another known expedient is to provide the tensile forces restraining the windings, in a concentric arrangement, against distortion due to stresses resulting from short circuit currents and the like by means of a cylinder of dielectric material arranged between the low voltage and high voltage windings. This particular arrangement has the disadvantage that the wall thickness of the cylinder must be great enough so that the cylinder will withstand very large forces due to short circuits. Such a cylinder is not only expensive, but also makes it very difiicult, from the standpoint of thermal and space considerations,

to solve the important heat dissipation problem in the main cooling channel between the windings.

While the problems mentioned above are encountered particularly with high voltage windings, analogous problems are encountered with respect to relatively low volttage and low power windings.

An object of the present invention is to provide a winding unit including at least one winding and pressing means for restraining the winding again-st distortion due to stresses resulting from short circuit currents and the like, and in which the tensile forces for the pressing means are produced, at least partly, by strip means of flexible material extending between and engaged with the two pressure elements of a pair and under tension to maintain the pressure elements pressed firmly against the winding.

Another object of the invention is to provide, in a winding unit as mentioned above, pressing means in which the tensile forces are produced at least partly by strips of dielectric material extending inside and outside the winding and interconnecting the pressure elements under tension.

A further object of the invention is to provide, in a winding unit of the type mentioned, pressure means in which the tensile forces are produced by strips of dielectric material, and in which the dielectric material may comprise, for example, a plastic reinforced with glass fibers.

Still another object of the invention is to provide, in a winding unit of the type mentioned, pressing means including tensile elements of dielectric material in the form of strips distributed uniformly around the circumference of the winding.

Still a further object of the invention is to provide, in

a winding unit of the type mentioned, pressing means in- I suring a reliable pressing of the winding and requiring very little space, and which pressing means does not adversely influence cooling of the winding and does not present any hazard with respect to flash-over.

Still another object of the invention is to provide a winding unit of the type just mentioned and including pressing means of the type mentioned in the preceding paragraph, in which no major radial shearing forces can act on the winding due to the fact that the tensile strips are highly flexible.

A further object of the invention is to provide, in a winding unit of the type mentioned in the preceding paragraph, pressing means including means for automatically equalizing the stresses in opposed tensile strips interconnecting the pressure elements. Another object of the invention is to provide, in a winding unit of the mentioned type and including pressing means of the mentioned type, tensile elements in the form of dielectric strips interconnecting the pressure elements and in which corresponding ends of a pair of strips are secured to opposite ends of an oscillatable rocker to equalize the tensions in the two strips.

Still another object of the invention is to provide, in a winding unit of the type mentioned and including pressing means of the type mentioned, and wherein the winding unit includes low voltage and high voltage windings, a common pressure means for the two windings in which tie rods of metal or dielectric material extend inside the low voltage winding and flexible dielectric bands extend outside the high voltage winding.

Still another object of the invention is to provide, in a low voltage, ready-to-use winding unit including pressing means of the type mentioned, tensile means interconnecting the pressure elements and comprising strips of dielectric material wrapped completely around the winding and the pressure elements at least once.

A further object of the invention is to provide a winding unit including at least one winding and pressing means of the type mentioned in the preceding paragraph, in which the ends of each strip are welded, glued or sewn together, or advantageously provided with adjustable connecting or closure means so that the length of the strip may be easily adapted to the dimensions of the winding.

Still a further object of the invention is to provide a winding unit including low voltage and high voltage windings and pressing means, and of the type mentioned above, in which the tensile strips are regularly spaced over the circumference of both windings, simultaneously embracing both windings, and with interposition of pressing elements conjoiutly engaging both windings,

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a partial radial cross sectional view, in a vertical plane, through a segment of an annular transformer winding provided with pressing means embodying the invention;

FIG. 2 is a detail of FIG. 1 looking in the direction AA;

FIG. 3 is a detail of FIG. 1 taken on the section line B-B;

FIG. 4 is a detail of FIG. 1 looking in the direction of the arrows CC;

FIG. 5 is a view similar to FIG. 1, illustrating a modification of the invention;

FIG. 6 is a partial radial cross sectional view, in a vertical plane, through a segment of concentric annular low voltage and high voltage windings provided with pressing means in accordance with the invention;

FIG. 7 is a perspective view, on an enlarged scale, or a detail of FIG. 6; and

FIG. 8 is an elevation view illustrating adjustable strip end connecting means in accordance with the invention.

Referring first to FIGS. 1 through 4, a winding 1 which, may be designed for a high powered transformer, an impedance coil, or the like, is confined or restrained by a number of pressing means distributed equally around its circumference. Each pressing means comprises a pressure segment 2 and a rocker 3, with segment 2 and rocker 3 being interconnected by strips 4 and 5 of dielectric material such as, for example, plastic reinforced with glass fibers. Winding 1 is positioned between wooden supporting segments 6 and supporting rings 7. Pressure segment 2 is provided with thumb screws 8 by means of which an arcuate pressure plate 9 can be pressed against ring 7 to set the desired restraining pressure for windin 1.

Rocker 3 comprises side plates 10 and 11 interconnected by semi-circular pivot shaft 12, and cross bars 13 and 14 at opposite ends. Pivot shaft 12 is seated in a corresponding recess in a wooden block 16 resting on a support 17 which may be mounted, for example, on the iron core of a transformer. Tension bands 4 and 5 are secured around the cross bars 13 and 14, respectively. Rocker 3 has sufficient play so that it can turn about the axis of shaft12 and thus adapt itself to any difference in the lengths of the strips 4 and 5.

Thus, when thumb screw 8 is operated to stretch the bands 4 and 5, any difference in tension between the two bands is compensated by the rocker 3. Such differences in length are, in practice, substantially unavoidable so that different stresses would be applied to the different bands or strips. If the strips are of different length, different tensile forces are produced in the strips when thumb screws 8 are tightened, and rocker 3 turns in one direction or the other until the forces in the strips 4 and 5 are exactly equal.

Referring now to FIG. 5, a winding unit is illustrated as including alow voltage winding 18 and a high voltage winding 20 'which'are restrained by common pressure segments 22. In this embodiment of the invention, tie rods or bars 19 of metal or dielectric material, interconnect the pressure segments inside the low voltage windings, and strips 21 of dielectric material interconnect the pressure elements or segments externally of the high voltage winding. If necessary, the other ends of the strips 21 may be connected to the ends of a rocker, as mentioned in connection with the embodiment of the invention shown in FIGS. 1 through 4. As a variation,

instead of thumb screws being utilized to adjust the pressure of the pressure elements 22, spring pressure elements 23 can be used. These spring pressure elements insure permanent tight pressing of the windings during operation, even if the dielectric strips 21 should expand with the passage of time.

In the embodiment of FIGS. 1 throughS the invention has been illustrated as applied to high power windings such as used with transformers, impedance coils and the like. However, the principles of the invention are applicable equally for windings of transformers, impedance coils or the like, of smaller power. In such instance, restraint of the winding is effected by means of strips of dielectric material wrapped completely around the winding and the pressing elements at least once. The ends of the strips may be welded, cemented or sewn to gether. Alternatively, the ends of the strips may be interconnected by a suitable closure or connecting means so that the length of the strip may be adapted easily to the dimension of the winding.

In the case of concentrically arranged low and high voltage windings, the strips may embrace both windings with the interposition of a joint pressing element, and are again distributed regularly around the circumference of the windings. The advantage of this embodiment of the invention, which is shown in FIGS. 6, 7 and 8, resides in insuring reliable restraint of the winding without use of metallic pressing elements, without requiring very much space, and without any danger of flash-overs. In concentrically arranged windings, the use of the invention restraining means does not interfere to any appreciable extent with heat dissipation in the main cooling conduit.

Referring more particularly to FIGS. 6, 7 and 8, a winding unit is illustrated as including a low voltage winding 31 and a high voltage winding 32 insulated from each other by a dielectric cylinder 33. Windings 31 and 32 are conjointly restrained by means of a number of pressing devices which are spaced regularly around the circumference of the Windings.

Each pressing device comprises an upper wooden pressing segment 34, a lower wooden pressing segment 35, and a strip 36 of dielectric material such as, for example, a glass fiber reinforced synthetic resin material,

this strip embracing both segments 34 and 35. The ends of each strip 36 are interconnected in any suitable manner. For example, as indicated at 38 in FIG. 6, the ends of a strip may be interconnected by welding or gluing.

Each strip 36 has guiding and bearing engagement in a rounded-off recess 37 (FIG. 7) of a segment 34 or 35, so that there will be no sharp curves or bends in the strip. Segments 34 and 35 also function as end insulation means between the Windings and the supporting elements at the iron core. Additionally, these segments form the structural connection between the windings and the supporting element.

Instead of the ends of each strip 36 being fixedly connected, they may be connected in a detachable and adjustable manner. Thus, and referring to FIG. 8, one end of each strip 36 has a pair of rings 39 and 40 anchored therein-as by having the end of the strip looped through the rings and cemented or otherwise secured to the body of the strip. In the manner shown in FIG. 8, the other end of each strip 36 is passed through both rings 39 and 40. The desired pressure may be adjusted by tightening the end of the strip 36, and the strip 36 will retain its tension since its parts 36a and 36b will lock against each other and against the ring 40. For increased security, the free ends 360 of the strip 36 may also be cemented or glued to the body of the strip.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. i

What is claimed is:

1. In a ready-to-use winding unit for mounting on a magnetic core and including at least one annular winding and pressing means engaged with the winding to restrain the same against distortion due to stresses resulting from short circuit currents and the like: the improvement in which said pressing means comprises at least one pair of pressure devices embracing diametrically opposite segments of the winding, each pressure device comprising a pair of pressure elements each engaging respective opposite end faces of the respective winding segment, tension means extending along the radially inner side and the radially outer side of each winding segment and connecting both pressure elements of each pressure device and under tension to maintain the connected pressure elements pressed firmly against the winding end faces, and tension equalizing means associated with the tension means of each pressure device; and in which, with respect to said tension equalizing means, one pressure element of each pressure device comprises a rocker; and means oscillatably mounting said rocker intermediate its ends; first ends of said tension means being anchored to opposite ends of said rocker whereby, when tension is conjointly applied through the second ends of said tension means, any difference in length of the tension means is equalized by said rocker.

2. In a ready-to-use winding unit, pressing means as claimed in claim 1, wherein said tension means includes metal bars interconnecting said pressure elements.

3. In a ready-to-use winding unit, pressing means as claimed in claim 1, wherein said tension means includes metal bands interconnecting said pressure elements.

4. In a ready-to-use winding unit, pressing means as claimed in claim 1, in which said winding unit comprises a pair of concentric annular windings, at least one of. said pressure devices being commonly engaged with and embracing both of said windings.

5. In a ready-tense winding unit, pressing means as claimed in claim 4, in which one of said windings is a low voltage Winding and the other of said windings is a high voltage winding.

6. In a ready-to-use winding unit, pressing means as claimed in claim 5, including tension means extending inside said low voltage winding and interconnecting the pressure of each device; and tension elements extending outside said high voltage winding and comprising dielectric strips.

7. In a ready-to-use winding unit, pressing means as claimed in claim 6, in which said tension means inside said low voltage winding are metal.

8. In a ready-to-use winding unit, pressing means as claimed in claim 6, in which said tension means inside said low voltage winding are of dielectric material.

References Cited UNITED STATES PATENTS 914,941 3/ 1909 Fortescue 336--199 X 1,600,963 9/1926 Brand 336---197 X 1,798,576 3/1931 Alonso 24197 2,892,168 6/1959 Siedel et a1. 336-499 X 3,135,888 6/1964 Coggeshall 336197 X FOREIGN PATENTS 180,614 12/1954 Austria. 297,030 7/ 1929 Great Britain.

DARRELL L. CLAY, Primany Examiner.

L. H. MYERS, Examiner.

D. A. TONE, Assistant Examiner. 

1. IN A READY-TO-USE WINDING UNIT FOR MOUNTING ON A MAGNETIC CORE AND INCLUDING AT LEAST ONE ANNULAR WINDING AND PRESSING MEANS ENGAGED WITH THE WINDING TO RESTRAIN THE SAME AGAINST DISTORTION DUE TO STRESSES RESULTING FROM SHORT CIRCUIT CURRENTS AND THE LIKE: THE IMPROVEMENT IN WHICH SAID PRESSING MEANS COMPRISES AT LEAST ONE PAIR OF PRESSURE DEVICES EMBRACING DIAMETRICALLY OPPOSITE SEGMENTS OF THE WINDING, EACH PRESSURE DEVICE COMPRISING A PAIR OF PRESSURE ELEMENTS EACH ENGAGING RESPECTIVE OPPOSITE END FACES OF THE RESPECTIVE WINDING SEGMENT, TENSION MEANS EXTENDING ALONG THE RADIALLY INNER SIDE AND THE RADIALLY OUTER SIDE OF EACH WINDING SEGMENT AND CONNECTING BOTH PRESSURE ELEMENTS OF EACH PRESSURE DEVICE AND UNDER TENSION TO MAINTAIN THE CONNECTED PRESSURE ELEMENTS PRESSED FIRMLY AGAINST THE WINDING END FACES, AND TENSION EQUALIZING MEANS ASSOCIATED WITH THE TENSION MEANS OF EACH PRESSURE DEVICE; AND IN WHICH, WITH RESPECT TO SAID TENSION EQUALIZING MEANS, ONE PRESSURE ELEMENT OF EACH PRESSURE DEVICE COMPRISES A ROCKER; AND 